12 thoughts on “Questions About NASA’s Heavy-Lift Plan”
As Clark says “we don’t have to show you no stinkin’ missions!”
I’m not sure how far along the RS-25E is (they’ve been talking about it for years), but they could just keep making the older reusable RS-25’s. Given the crazy nature of these programs, the older RS-25 (the SSME) will probably be less expensive than its cheap, expendable version.
One thing I do like about their proposal is that it looks like it has growth potential. By moving the SSME engines over to some sort of re-usable winged orbital vehicle, which could be mounted to the side of the external tank, they could save the cost of the engines. Give it a delta wing for cross range performance and a large payload bay, and… Oh, wait.
They haven’t made an SSME in decades. They wouldn’t know how.
Mr. Turner, let me finish that thought for you… And then you have an orbiter with a 2% rate of lethal failures (that also destroy the vehicle), with a ground crew of 60,000, turn-around time of six months, a billion dollars per launch and that can’t perform missions beyond LEO. Brilliant!
I think the return to flight after the Columbia disaster used one new SSME, which was in 2005. Most of the current ones probably date from the 90’s or early 2000’s. They’ve built 47 of them, as each engine is only used six or so times, with some just used for one flight. I have no idea what NASA did with their early block I engines, but I’d guess they were torn down and analyzed.
They could still try to re-use the engines in this new configuration if they’d design the engine section to seperate from the fuel tank, making the assembly similar to a standard re-entry capsule but with the heat shield between the engines and tank. Running the plumbing through a heat shield shouldn’t pose a problem because the Shuttle already does that.
Some of the early Shuttle concepts had the engines on the external tank, which is far superior for launch, but they couldn’t figure out how to swing the engines over the orbiter so they could re-use them. If the engines were attached to the tank and then seperated to re-enter by themselves then it would’ve eliminated a great deal of extra weight and complexity from the aft end of the Shuttle, plus allowing a more streamlined tail for a better glide ratio. It would’ve significantly cut the orbit weight of the Shuttle, which would’ve allowed it to have greater delta-V in orbit. It also would’ve reduced the Shuttle’s turn-around time because the engines would be back on the ground a week or two before the Shuttle landed, and having multiple engine pods per Shuttle would seperate the Shuttle refurbishment schedule from the engine schedule.
Of course such redesigns and improvements should’ve been done in the 80’s, to give us Shuttle version II, which should’ve led to Shuttle version III in the 90’s, and Shuttle IV in the 00’s. Instead we just tried to use the first concept forever.
That would be SN-2055 1 which flew on STS-112. “New” means it hadn’t been flown before.. but it was built decades ago.
Just keeping the original engines running was a chore. The spare parts are kept in storage because there’s nowhere to buy them.
Honestly, the idea that new SSMEs can be built is absurd.. John Shannon has been saying this since Griffin proposed using them for the upper stage of the Ares I. As for some new expendable version of the SSME, they’ve been talking about it *but not funding it* since the beginning of the program.
Making a new engine makes more sense.. of course the fact that US industry is screwing around with staged combustion hydrocarbon engines from Russia instead of their own designs suggests that they’re incapable of doing that too.
Why? It’s called youth. SpaceX has it, P&WR don’t.
Or, I guess I should have said, “as reported yesterday” but it looks like the fire was on the 9th.
Trent, I hadn’t realized they’d leave a new SSME sitting around for that long, but I guess it makes sense because the used engines have been proven, while the new one had no flight history and thus might’ve represented more of a risk.
I agree that legacy rocket engine companies might not be the way to go. For something to meet the SLS requirement, I would think a LOX/LH2 engine in the 3 million lbf class would be desirable as a first stage (like some doubling of the Rocketdyne M-1, which was abandoned). That would give you a booster good for half the 130 tons (the intial requirement), then add strap-ons to meet the minimal 130 ton requirement, then use it as a second stage if you want to launch really big things.
NASA’s 5 SSME idea throws away what, $400 million in engines?
But as things stand, a new Rocketdyne engine in that class would cost a fortune.
Josh, don’t you think it’s strange that after all the rocket engine development this country did in the 50’s and 60’s, we’re now using moon-race era engines that the Russians found abandoned in a warehouse?
Don’t forget Merlin and RS-68.
If you want to chart the progress of a disposable SSME, look no further than the RS-68. History often repeats itself. Its evolution was no accident, nor was its cost structures that it as well as others carry along. Be careful what you wish for in a new engine for you may get it.
As to why we use Russia as our “go to” source for engines, look back at the long list of engine development cancellations, how sparsely the total inventory is used, account for all the corporate mergers – mergers do not make for more efficient corporations nor are they less costly then competition. The Russians have had the same troubles that we have had in this activity – they just completed more projects and warehoused them better. We’re living off their leavings – its easier/cheaper to raid their warehouse than dig through our ash heaps/junkyards.
We’ve also had the habit of starting an engine to fit a overly specific need, rather than do an specific engine and then build a vehicle around it. The Russians have more unsuccessful vehicles to draw on.
So where’s the success so far with SpaceX’s Merlin? Might it be an example of reusing something more times (“economy of design application”), in cost reducing its commonality so its cost structure don’t protrude into each of those applications, and resisting efforts to let parasitic technologies that might add more cost for less gain enter into the design. What would these suggest to the “going forward” process for Teledyne Brown and Aerojet? Or PWR?
By the way, you could do a lot worse than starting off with a NK-33/43. Or a SSME.
Or for that matter a FASTRAC.
The Merlin is low cost, but the RS-68 is still $20+ million a copy.
Perhaps the Falcon 9 Heavy concept of cross feeding should be pursued to its logical conclusion, keeping in mind that the high pressure turbopumps are the expensive part.
Design a single, expensive, efficient, HP turbopump that can run all 27 1st stage Merlins as simple pressure-fed engines. The two strap ons pump LP fuel to the center tank. The center tank pumps LP fuel up to a tank in the third stage or the orbital vehicle, where the big HP turbo pump is located (it’ll stay with the vehicle so it gets re-used). You just have to have piping run from top of the rocket to the bottom, with cutoff valves in between stages and T-junctions and cutoff valves for the intermediate stages.
At launch, the big HP pump starts up and provides power to the LP pumps that move the fuel around. The first stage and strap-on engines are pressure fed from the top of the rocket where the turbopump is located. The strap ons are expended and the HP pump slows down, with the only draw being the first stage. It continues to throttle down to limit G forces toward as the first stage fuel is consumed. Then valves in the second stage close to cut off the fuel flow heading down to the first stage engines (which leaves some loss in the long feed pipes). After seperation, smaller valves open to the second stage engines, also pressure fed, with the HP turbopump running almost at idle. As the second stage is depleted the main valves that fed HP fuel from the turbopump to the first and second stages close, and after seperation it can run a third stage, if needed.
So you’re throwing away injectors, combustion chambers, nozzles, piping, LP pumps, and tanks, but running the whole stack from a single, reusable HP turbopump.
As Clark says “we don’t have to show you no stinkin’ missions!”
I’m not sure how far along the RS-25E is (they’ve been talking about it for years), but they could just keep making the older reusable RS-25’s. Given the crazy nature of these programs, the older RS-25 (the SSME) will probably be less expensive than its cheap, expendable version.
One thing I do like about their proposal is that it looks like it has growth potential. By moving the SSME engines over to some sort of re-usable winged orbital vehicle, which could be mounted to the side of the external tank, they could save the cost of the engines. Give it a delta wing for cross range performance and a large payload bay, and… Oh, wait.
They haven’t made an SSME in decades. They wouldn’t know how.
Mr. Turner, let me finish that thought for you… And then you have an orbiter with a 2% rate of lethal failures (that also destroy the vehicle), with a ground crew of 60,000, turn-around time of six months, a billion dollars per launch and that can’t perform missions beyond LEO. Brilliant!
I think the return to flight after the Columbia disaster used one new SSME, which was in 2005. Most of the current ones probably date from the 90’s or early 2000’s. They’ve built 47 of them, as each engine is only used six or so times, with some just used for one flight. I have no idea what NASA did with their early block I engines, but I’d guess they were torn down and analyzed.
They could still try to re-use the engines in this new configuration if they’d design the engine section to seperate from the fuel tank, making the assembly similar to a standard re-entry capsule but with the heat shield between the engines and tank. Running the plumbing through a heat shield shouldn’t pose a problem because the Shuttle already does that.
Some of the early Shuttle concepts had the engines on the external tank, which is far superior for launch, but they couldn’t figure out how to swing the engines over the orbiter so they could re-use them. If the engines were attached to the tank and then seperated to re-enter by themselves then it would’ve eliminated a great deal of extra weight and complexity from the aft end of the Shuttle, plus allowing a more streamlined tail for a better glide ratio. It would’ve significantly cut the orbit weight of the Shuttle, which would’ve allowed it to have greater delta-V in orbit. It also would’ve reduced the Shuttle’s turn-around time because the engines would be back on the ground a week or two before the Shuttle landed, and having multiple engine pods per Shuttle would seperate the Shuttle refurbishment schedule from the engine schedule.
Of course such redesigns and improvements should’ve been done in the 80’s, to give us Shuttle version II, which should’ve led to Shuttle version III in the 90’s, and Shuttle IV in the 00’s. Instead we just tried to use the first concept forever.
That would be SN-2055 1 which flew on STS-112. “New” means it hadn’t been flown before.. but it was built decades ago.
Just keeping the original engines running was a chore. The spare parts are kept in storage because there’s nowhere to buy them.
Honestly, the idea that new SSMEs can be built is absurd.. John Shannon has been saying this since Griffin proposed using them for the upper stage of the Ares I. As for some new expendable version of the SSME, they’ve been talking about it *but not funding it* since the beginning of the program.
Making a new engine makes more sense.. of course the fact that US industry is screwing around with staged combustion hydrocarbon engines from Russia instead of their own designs suggests that they’re incapable of doing that too.
Why? It’s called youth. SpaceX has it, P&WR don’t.
Looks like the AJ-26 motor encountered a mishap in its testing yesterday. Understandably this is what testing is for but hopefully it won’t impact schedules too badly.
Or, I guess I should have said, “as reported yesterday” but it looks like the fire was on the 9th.
Trent, I hadn’t realized they’d leave a new SSME sitting around for that long, but I guess it makes sense because the used engines have been proven, while the new one had no flight history and thus might’ve represented more of a risk.
I agree that legacy rocket engine companies might not be the way to go. For something to meet the SLS requirement, I would think a LOX/LH2 engine in the 3 million lbf class would be desirable as a first stage (like some doubling of the Rocketdyne M-1, which was abandoned). That would give you a booster good for half the 130 tons (the intial requirement), then add strap-ons to meet the minimal 130 ton requirement, then use it as a second stage if you want to launch really big things.
NASA’s 5 SSME idea throws away what, $400 million in engines?
But as things stand, a new Rocketdyne engine in that class would cost a fortune.
Josh, don’t you think it’s strange that after all the rocket engine development this country did in the 50’s and 60’s, we’re now using moon-race era engines that the Russians found abandoned in a warehouse?
Don’t forget Merlin and RS-68.
If you want to chart the progress of a disposable SSME, look no further than the RS-68. History often repeats itself. Its evolution was no accident, nor was its cost structures that it as well as others carry along. Be careful what you wish for in a new engine for you may get it.
As to why we use Russia as our “go to” source for engines, look back at the long list of engine development cancellations, how sparsely the total inventory is used, account for all the corporate mergers – mergers do not make for more efficient corporations nor are they less costly then competition. The Russians have had the same troubles that we have had in this activity – they just completed more projects and warehoused them better. We’re living off their leavings – its easier/cheaper to raid their warehouse than dig through our ash heaps/junkyards.
We’ve also had the habit of starting an engine to fit a overly specific need, rather than do an specific engine and then build a vehicle around it. The Russians have more unsuccessful vehicles to draw on.
So where’s the success so far with SpaceX’s Merlin? Might it be an example of reusing something more times (“economy of design application”), in cost reducing its commonality so its cost structure don’t protrude into each of those applications, and resisting efforts to let parasitic technologies that might add more cost for less gain enter into the design. What would these suggest to the “going forward” process for Teledyne Brown and Aerojet? Or PWR?
By the way, you could do a lot worse than starting off with a NK-33/43. Or a SSME.
Or for that matter a FASTRAC.
The Merlin is low cost, but the RS-68 is still $20+ million a copy.
Perhaps the Falcon 9 Heavy concept of cross feeding should be pursued to its logical conclusion, keeping in mind that the high pressure turbopumps are the expensive part.
Design a single, expensive, efficient, HP turbopump that can run all 27 1st stage Merlins as simple pressure-fed engines. The two strap ons pump LP fuel to the center tank. The center tank pumps LP fuel up to a tank in the third stage or the orbital vehicle, where the big HP turbo pump is located (it’ll stay with the vehicle so it gets re-used). You just have to have piping run from top of the rocket to the bottom, with cutoff valves in between stages and T-junctions and cutoff valves for the intermediate stages.
At launch, the big HP pump starts up and provides power to the LP pumps that move the fuel around. The first stage and strap-on engines are pressure fed from the top of the rocket where the turbopump is located. The strap ons are expended and the HP pump slows down, with the only draw being the first stage. It continues to throttle down to limit G forces toward as the first stage fuel is consumed. Then valves in the second stage close to cut off the fuel flow heading down to the first stage engines (which leaves some loss in the long feed pipes). After seperation, smaller valves open to the second stage engines, also pressure fed, with the HP turbopump running almost at idle. As the second stage is depleted the main valves that fed HP fuel from the turbopump to the first and second stages close, and after seperation it can run a third stage, if needed.
So you’re throwing away injectors, combustion chambers, nozzles, piping, LP pumps, and tanks, but running the whole stack from a single, reusable HP turbopump.